This invention relates to an electronic musical instrument and, more particularly, to an electronic musical musical instrument capable of repeatedly producing the same amplitude envelope of a musical tone.
The amplitude envelope of a musical tone herein signifies a series of temporal change of a musical tone amplitude from the start of generation of the musical tone to the end of it. The series of the envelope shape includes at least an attack portion or a rise portion of the tone and a decay portion or a fall portion thereof. When a tone is sounded, its amplitude envelope normally starts from the attack portion and ends in the decay portion. There occurs a case, however, where performance of a musical piece requires a musical effect which may be termed an "attack repeat effect." This musical effect can be obtained by producing an envelope shape starting from the attack and ending in the decay repeatedly during a single continued production of a musical tone and controlling the amplitude of the musical tone by such envelope shape. The attack repeat effect is a musical effect which gives an impression as if the tone being played stopped and started periodically in succession.
There is a prior art electronic musical instrument which can produce such attack repeat effect by employing a time constant circuit comprising a capacitor and a resistor for generating an envelope shape. In the prior art instrument, electronic charge must be supplied periodically to this time constant circuit for repeatedly producing the envelope shape. The envelope obtainable by the prior art instrument is limited in its shape. Moreover, if a multi-channel system is used, the prior art instrument requires the time constant circuit for each of the plural channels resulting in an extremely complicated construction.